[Int-area] MPT Network Layer Multipath Library (draft-lencse-tsvwg-mpt-00.txt)

[Gabor Lencse <[e-mail]>]

Dear INTAREA WG members,

I am Gabor Lencse, the first author of a "-00" draft about the MPT 
Network Layer Multipath Library: 
https://tools.ietf.org/html/draft-lencse-tsvwg-mpt-00

It was introduced to the INTAREA WG by our co-author Marius Georgescu at 
IETF 99.

I would like to elaborate on the feedback we received during the 
presentation.

Q1 (David, from Apple): What is the motivation, what you are trying to 
solve? Why are you trying to use multiple interfaces?

A1: Throughput aggregation between two sites. (E.g. between data centers)

My answer:

The problem to  be solved is the following. Due to the design of the 
TCP/IP protocol stack and its socket interface, even if a device has 
multiple network interfaces, only one of them can be used for a 
communications session. And it is a serious limitation many times!

Example: Somebody is remotely participating at an IETF meeting using 
Meetecho on his laptop using WiFi connection (to save costs). When he 
receives permission to ask a question, the WiFi connection brakes. By 
the time he manages to switch over to LTE, it is too late.  -- According 
to our tests, MPT can do the switchover seamlessly.

How common is this situation? I think many people have smartphones, with 
WiFi and LTE, and uses WiFi when available in order to save costs. Many 
of them use free video calls (e.g. by Skype, Viber, WhatsApp, etc.) and 
would be happy if the free WiFi could be backed up by seamless 
switchover to LTE during the calls.

There are a number of multi path solutions, which shows that the problem 
is real, but I contend that MPT differs from them and MPT can be more 
suitable for certain purposes than they for different reasons:

- MPTCP [RFC6824] is good, but it is "built together" with TCP. Some 
applications, e.g. DNS resolution or RTP use UDP. (They can work well 
with MPT.)

-  Huawei's GRE Tunnel Bonding Protocol [RFC8157] was designed for this 
very purpose, but it uses GRE, which is filtered out in many networks. 
(MPT uses GRE-in-UDP, thus MPT behaves as a standard UDP application in 
the carrier networks.)

- BANANA https://tools.ietf.org/html/draft-leymann-banana-data-encap-00 
aims to do bandwidth aggregation, but it also uses GRE and not 
GRE-in-UDP. And I am not sure if it is able to provide a resilient 
tunnel (that is switching over from a given underlying path to another one).

- Load Sharing for SCTP 
https://tools.ietf.org/html/draft-tuexen-tsvwg-sctp-multipath-14 is also 
a multipath solution, but it is very specific. MPT provides an IP 
tunnel, which can be used for any purpose.

All in all, I could not find any other solutions that would provide such 
flexible, multipurpose IP tunnel (providing both IPv4 and IPv6), which 
is both resilient and can aggregate the transmission capacity of several 
(even high number of) underlying paths, and which can be used in any 
networks, where UDP is carried over either IPv4 or IPv6. I would be 
interested in hearing about any similar solutions.

And I would like to receive your feedback about MPT. All your questions, 
comments, suggestions, etc.

Best regards,

Gabor